Yea, the similarities are there and they are evident.
There's nothing wrong about being impressed with another author work. The point is that sometime some concepts and ideas influence us so deeply that we need an external output to point them out.
As Wetcircuit and Thomo already said in the comments, the problem here is that while you believe those characters are different, the audience may not and they'll probably find that fastidious. As you stated:
- Both the main characters share the fancy name "Kaz"
- Both share an imposing nickname with dark overtones
- Both have the same simbolic crow-headed cane
- Both have a close connection with a female (lead ?) character who owes them
- Both those female characters have a romantic interest in the respective "Kaz"
- Both those female characters work in a pleasure house
It doesn't really matter if those things came to be in a different way (e.g., you mentioning the difference between the Inej owing an actual debt, while Violet a debt of gratitude). Probably your character are meant to be different, but either:
You are being influenced by Six of Crows more than you think you are, and you're making your character similar, without almost being aware of it.
Your character are different, but it's difficult to see through all the similar situations and imagery they have in common with the other couple.
It's as simple as that. In the end, only you can give an answer to this question, since you have the full scope of the story in mind. One similarity is pure chance, two might be a coincidence, three are homage ... four is a copy.
Think deeply who those characters are. What's their purpose, what they mean, what's their role to play in the story.
Then compare your findings with your understanding of Bardugo's characters. Do they share the same role? Ambitions? Mannerism? Goal? Personality? Backstory in general (avoid the specific details)?
It's fine if the answer of some of those questions is yes; it's not fine if they all are.
If there is some major problem of imitation, you should be able to rule that out here and do some serious character redesign.
If you surpass that phase, you'll hopefully have a core set of differences. Ask yourself how those should come into play in the story. Maybe the differences didn't impress your reader. Maybe they aren't so evident. You don't have to struggle to show that your Kaz is not Bardugo's Kaz: if some core difference is there, from the previous step, it should be self-evident. So maybe there's something about your characters that you didn't write about enough, something that you've omitted. Maybe you've focused on the wrong concepts. Your characterization may be different, but the reader is led astray by the fact that there are some many visual cues reminiscent of Six of Crows.
So, the last phase would be rework on those visual cues. I'm suggesting doing this last because you don't want to turn your crow-headed cane into a raven-headed cane and leave everything else as is. It wouldn't solve a thing, if there is a problem in the previous two stages. But, if you are confident you've passed those, it's time to consider why you have to keep all those superficial similarities; yea, they are superficial, but then again, since they are not core concepts, why bother with keeping them? There should be some that you can change, exploring some other concept instead.